The present invention relates generally to wheel support assemblies for vehicular tires and more particularly to the center hub portion thereof, especially one of the design disclosed in Assignee""s Fitz et al U.S. Pat. No. 6,042,194 which is incorporated herein by reference.
An overall wheel structure or wheel support assembly is designed to be mounted to the end plate of a vehicular axle and typically includes a hub as well as an arrangement of spokes and a rim for receiving a tire. The hub itself typically includes an arrangement of bars which have outwardly-most extending ends and which are connected to one another to form a hub body. The hub body, in turn, defines (1) a common center point and (2) an overall contact face defined in part by the bars.
In the past, there has not been much consideration given to the shape of the hub, much less the area that is in contact with the end plate of a vehicle""s axle. Others have taken it for granted that any shape that has holes for the lug bolts will suffice as long as there is sufficient material to bolt to. As will be seen hereinafter, this has led to the previous designs that have shapes on the ends of the bars which are not so rounded and which define a relatively large radius substantially equal to the distance from the center of the hub to the ends of the bars. Applicants have discovered that this configuration leads to very high peak stresses in the material, and makes the use of relatively ordinary carbon steel difficult if not impossible.
The present invention overcomes or at least reduces the stress problems just mentioned by providing a hub designed in accordance with the present invention. The hub, as will be seen, comprising: a plurality of bars which have outwardly-most extending ends, each end of which displays a predetermined curvature. the bars being connected to one another to form a hub body defining (1) a common center point and (2) an overall contact face defined in part by said bars; the contact face including outwardly-most extending ends corresponding to the ends of the bars and displaying predetermined curvatures corresponding to the outwardly-most extending ends of the bars, the predetermined curvatures of the ends of said contact face displaying radii of curvature smaller than the distance from said center point of the contact surface to the outwardly-most extending ends of said bars; each of the bars having a through hole (1) which is adapted to receive an axle bolt and (2) which extends in a direction perpendicular to said contact face such that, when the wheel structure is mounted to said vehicular axle, the contact surface is contiguous with the axle end plate.
As a specific example, applicants have discovered that by reducing the radius of curvature of the ends of the bars there is a significant reduction in the peak stresses in the material. Peak stresses were reduced analytically by as much as 32% over the previous design. A design that can reduce these peak pressures could allow the use of lighter or less expensive materials. Lighter materials would make assembly by stamp forming the hub assembly from a single sheet of material easier thereby possibly making the cost of the assembly go down, and at the same time, a lighter assembly will also make a vehicle more fuel efficient. Another advantage of a stress reducing design is that the wheel assembly can yield higher performance without adding weight.